Register file and method for designing a register file

Abstract

A register file includes a plurality of registers for storing therein data, a plurality of input ports for receiving therethrough the data to be stored in the registers, and a plurality of output ports for delivering therethrough the data stored in the registers. Each register includes an input port selector for selecting one of the write ports through which data is received. The register file also includes a read data selector block for specifying which data stored in the registers is to be read through one of the output ports. The output port selector is implemented by a combinational circuit which saves power dissipation of the register file.

1. A register file comprising:
 a plurality of input ports each for receiving therethrough a write data and having a priority order specified among said input ports; and 
 a plurality of registers each for storing therein said write data based on a write address, each of said registers including an input port selector and a data storage for storing an output from said input port selector, said input port selector including a combinational circuit including a plurality of first AND gates each corresponding to one of said input ports and a first OR gate for generating a logical sum of outputs from said first AND gates, wherein: 
 each of said first AND gates in one of said input port selector receives a write instruction signal for specifying whether or not write data input through a corresponding one of said input ports is to be stored in a corresponding one of said registers, and generates a logical product of said write data and said write instruction signal and an inverted signal of each of said write instruction signals received through said input ports each having a higher priority order compared to said input port corresponding to said one of said input port selector. 
 
     
     
       2. The register file according to  claim 1 , further comprising a plurality of output ports and a plurality of output port selectors each for corresponding to one of said output ports, wherein each of output port selectors includes second AND gates each disposed corresponding to one of said registers for generating a logical product of data stored in a corresponding one of said registers and an activating signal assuming a high level upon selection of said corresponding one of said register and a second OR gate generating a logical sum of outputs from said first AND gates. 
     
     
       3. The register file according to  claim 1 , wherein said data storage includes a synchronous D-FF including a master latch for latching an output from said first OR gate, and a slave latch for receiving data from said master latch. 
     
     
       4. The register file according to  claim 1 , wherein said write instruction signal is generated by a logical product of a decoded signal decoded from said write address to have bits in number corresponding to the number of said registers and a write enable signal specifying whether or not each of said input ports is allowed to write data.